Keyboard printer character selection unit

ABSTRACT

In the linkage employed to control displacement of a print head for a keyboard printer to advance different characters into the printing position, an electromagnetic character selection unit is mounted in direct association with the linkage to control displacement of the print head through energization of a selected combination of solenoids over a limited time interval of each print cycle. Armature plates in the selection unit are quickly and accurately responsive to energization of the solenoids in activating the linkage, and the need for separate restoring elements or holddown mechanisms is avoided by an electronic switch which is correlated in opening and closing with the print cycle timing member whereby the solenoids can be deenergized well in advance of the end of each cycle and be self-restoring ahead of the next cycle.

O United States Patent 1 1 3,623,585

[ Inventor y Mmn 3,355,000 11/1967 Blodgett 197/17 Mo ntalnview, Calif- 3,391,774 7/1968 Greer 197/19 [21] APP ,471 3,452,851 7/1969 Holmes 197/19 Filed J 3,452,852 7/1969 Twardzik. 197/19 Paltf'med NOV-30,1971 3,453,379 7/1969 Holmes 197/19 X [73] Asslgnee 2335;552:732? Primary Examiner-Edgar S. Burr Attorney-John E. Reilly [54] SS PRINTER CHARACTER SELECTION ABSTRACT: In the linkage employed to control displacement 5 Claims Drawing Figs of a print head for a keyooard pr nter to advance different characters Into the printmg posttlon, an electromagnenc [52] U.S. Cl 197/19 character selection unit is mounted in direct association with [51] Int. Cl 341,] 5/30 the linkage to control displacement of the print head through [50] Field of Search 197/19, 98 energization of a selected combination of solenoids over a limited time interval of each print cycle. Armature plates in [56] Rderences Cited the selection unit are quickly and accurately responsive to UNITED STATES PATENTS energization of the solenoids in activating the linkage, and the 3,082354 3/1963 B k et u 197/19 need for separate restoring elements or holddown mechanisms 3,1 7,618 7/1965 Stanley et al. [97/20 X is avoided by an electronic switch which is correlated in open- 3.233,715 2/1966 Flieg 197/19 s and closing with the P cycle liming member whereby 3 294,1 17 12 19 gichemeyer et aL 97 9 X the solenoids can be deenergized well in advance of the end of each cycle and be self-restoring ahead of the next cycle.

PATENTEUNUV 30 I97] 3,623,585

SHEET 2 BF 2 INVEN'IH m. ROY G. MASON (w r/jgi ATTORNEYS KEYBOARD PRINTER CHARACTER SELECTION UNIT This invention relates to typewriters, and more particularly relates to a novel and improved character-selecting mechanism for operating a keyboard printer automatically in response to remotely applied electrical signals.

Keyboard printers have been developed in the past which have incorporated the necessary mechanism to cause the unit to print automatically in response to electrical signals received from a remote station, such as, a magnetic or paper tape. For

example, U.S. Pat. No. 2,919,002 granted to L. E. Palmer and No. 3,082,854 granted to Frank E. Becker et al. set forth a character selection mechanism of the type described. Generally, in systems of this type, a typewriter has a spherical print head bearing columns and rows of characters, each character being selectively advanced into position by rotation and tilt of the print head in response to actuation of a key lever. The rotation and tilt of the print head are mechanically controlled by a displacement mechanism, the latter being actuated by linkage set in motion by the depression of each key lever on the typewriter. This linkage typically comprises a character interposer movable in response to depression of each key to actuate one or more selector balls and latch interposers in predetermined combinations representative of the key or character; and through a series of selector latches in the displacement mechanism will determine the degree of rotation and tilt ofthe print head.

Correspondingly,, series of electrical pulses or signals representative of each character may be played back from a remote station to a series of electromagnets or solenoids associated with the latch interposers. Each pulse of a combination representing a character will energize a solenoid and, through the latch interposers, will control rotation and tilt of the print head to present the character for printing. In order to control the printing rate a cycle shaft is utilized in cooperation with a relay-controlled mechanism to hold down the latch associated with each of the electromagnets energized over the full period of the printing cycle for each character and to mechanically release the interposers at the end of the cycle.

In order to accelerate the automatic printing operation in accordance with the present invention, it is desirable that the electromagnets or solenoids be selectively energized to activate associated latches and that the latches be held down electrically over but a limited period of the cycle established for selecting and printing the character in response to the signal applied. In this way, the latch may be released ahead of the end of the cycle without necessity of a mechanical holddown or release for each latch, and the entire printing operation is speeded up with faster response, major simplification and reduction in size of the character selection unit, together with closer logic control.

It is therefore an object of the present invention to provide a novel and improved character selection unit for a keyboard printer, specifically a keyboard printer of the type utilizing a spherical pring head movable in relation to a stationary platen.

It is another object of the present invention to accelerate speed of selection and printing of a character on a typewriter automatically in response to signals applied from a remote point or station.

It is a further object of the present invention to provide a compact electromagnetic character selection unit for a keyboard printer being characterized by a reduction in number of parts and simplification of the selection procedure with close rapid control over selection and printing of each character.

In accordance with the present invention, electrical signals representative of each character to be printed are applied in each print cycle of the keyboard printer to energize selected ones of a group of solenoids. Each solenoid activates an associated latch in the print head displacement mechanism by controlling the pivotal movement of an armature plate which extends from connection with each latch through alignment with slots in the frame assembly for the solenoids and which is pivotal within one of the slots about the frame. The period of energization of the solenoid within each cycle is independently regulated by an electronic switch so that the plate is released ahead of the end of the print cycle and is self-restoring to permit the latch to return to its original disposition as a preliminary to the next cycle in succession. The improved mounting of the armature plates in relation to the latches, coupled with close accurate control over their activation within a limited period of each print cycle, serves to accelerate the entire printing operation and to obviate the use of special restoring mechanisms for the latch or plate members,

The above and other objects, advantages and features of the present invention will become more readily understood and appreciated from a consideration of the following detailed description of the present invention when taken together with the accompanying drawings, in which:

FIG. 1 is a perspective view of a conventional form of typewriter mechanism.

FIG. 2 is a perspective view showing the interrelationship of the electromagnetic character selection unit of the present invention with the mechanism shown in FIG. 1.

FIG. 3 is a view in detail of a portion of a preferred form of solenoid assembly and its connection to a latch interposer.

FIG. 4 is a somewhat schematic view of a filter switch in detail forming part of the electromagnetic character selection unit.

Referring in detail to the drawings, the preferred form of the present invention may be best characterized and described by reference to its use in association with a single print element typewriter, such as, that shown and described in U.S. Pat. to L. E. Palmer No. 2,919,002 Generally, a spherical print head 10 is selectively tilted and rotated to present a selected character on its surface for printing either manually by depression of a key lever 12 about a shaft 13, as shown in FIG. 1, or the same can be accomplished automatically by an electromagnetic character selection unit, as shown in FIG. 2, the latter being done in accordance with the present invention.

conventionally, depression of the key lever 12 or energization of the character selection circuit operates through a displacement mechanism, not shown, having two main portions, one for tilting and one for rotating the print head, in order to advance the desired character on the print head 10 into position for printing. As illustrated, whenever a key lever 12 is depressed by its key button 15, a pawl 16 on the key lever 12 engages a character interposer 17 to slidably advance the interposer and in turn to cause movement of selector bails 20, the latter being disposed for engagement by lugs 21 on the character interposer. Each character interposer has a different lug spacing so that different combinations of selector bails are advanced in response to depression of each key lever or, in other words, each combination of any one or more of the selector bails is representative of a character on each of the key buttons. Similarly, the selector bails each will impart movement to an associated latch interposer 24, there being seven latch interposers with each having a pivotal rod 25 to control movement of one or more selector latches, designated L, out of the path of a common actuating bail 26. Each latch interposer is biased in a rearward direction by a spring 25, and each selector latch is biased rearwardly into the path of the bail 26 by a spring 27. The actuating ball 26 is caused to be moved downwardly against those selector latches not removed from its path by the latch interposers, and those latches engaged will operate through the displacement mechanism to advance the character corresponding to the key lever depressed into position for printing.

In order to correlate advancement of the actuating bail 26 with movement of the selector latches, each character interposer 17 has a special lug 28 which when depressed will strike a cycle bail 29, forcing the bail 29 to move downwardly and through link 30 to cause pivoting of latch 31. A clutch sleeve 32 is released in response to pivoting of the latch 31 to actuate a clutch member 34 for rotation of a cycle shaft 35. In each print cycle the cycle shaft rotates 180 and through gearing 36, 37 and 38 is operative to correspondingly rotate a filter shaft 40 through l. As illustrated, the filter shaft 40 has diametrically opposed blades positioned beneath character interposers so that in each 180 filter shaft is engageable with a shoulder 42 on the character interposer in a direction to advance one or more of the selector bails in the manner previously described.

As shown in FIG. 2, the selector latch actuating bail 26 is conventionally in the form of a pivotal frame including rollers 44 on either side which are biased upwardly by a spring 45 into contact with cycle shaft cams, not shown. Thus, as the cycle shaft is rotated through each 180 print cycle the cams will operate through the rollers to force the bail to pivot downwardly about its shaft, causing displacement of those selector latches not moved out of position, to actuate the displacement mechanism. It will be evident that other parts and elements are associated with the character selection mechanism described to insure proper correlation between the selector latches, actuating bail, cycle shaft and filter shaft in the printing of each character, it being understood that the foregoing is intended more as a setting and introduction to the present invention.

The print head can be advanced to print a selected character in a corresponding manner under the control of the displacement mechanism electrically by the transmission of a combination of pulses, each combination being representative of a character to be printed. Here the pulses are applied to a series of solenoids 50, there being a solenoid 50 associated with each latch interposer 24 and selector latch L. As illustrated in FIGS. 2 and 3, the solenoids 50 are mounted in a U- shaped frame 52, the frame being supported on mounting brackets 53 beneath the latch interposers 24. Upper and lower extension plates 54 and 55 project forwardly from opposite sides of the frame 52, the extension plates being provided with a series of slots 56 and 57, a pair of slots being aligned on opposite sides of each solenoid to receive the free end of an armature plate 58. The slots are each of generally rectangular configuration and slightly overlap the side edges of the frame as shown, the slots being larger than the cross-sectional size of the plates so that each plate 58 is free to move a limited distance through each pair of slots toward and away from a solenoid. Each plate continues upwardly from the solenoid frame 52 into a curved or offset portion 59 and terminates in an upper relatively fiat end portion 60. The upper terminal end portion 60 of each plate 58 is bifurcated or otherwise formed for connection to a clevis 61 on each interposer rod 25 by means of a ringlike spacer 62. Each plate 58 is free to undergo movement in aligned slots 56 and 57 from a normal position at rest away from its associated solenoid to an inward position, under the attraction of the solenoid, against the side edges of the frame. It will be noted that the armature plate 58 when drawn toward the solenoid will rock about the upper side edge of the frame 52 under sufficient force to overcome the bias of the latch interposer spring 25' to move the rod member 25 forwardly and withdraw the selector latch away from the path of the latch-actuating bail 26. Conversely, when the solenoid is deenergized, the latch spring and latch interposer spring will force the plate to follow rearward movement of the latch interposer in returning the selector latch L to its original position of rest, the armature plate rocking, in an opposite direction about the upper side edge of the frame and away from the solenoid. The guide slots 56 and 57 in cooperation with the side edges of the frame will limit movement of the armature plates as well as the latch interposers and latches within very close tolerances. Accurate adjustment of the armature plates may be readily made by bending the curved portions 60 of each armature plate, each plate being of limited flexibility to permit its proper disposition in relation to the solenoid and latch interposer.

In order to energize and deenergize the solenoid assembly, solenoid or magnet drivers 44 are represented schematically on a printed circuit board 65 mounted beneath the interposer mechanism forwardly and to one side of the solenoid assembly. The printed circuit board 65 contains the necessary circuitry to interface the electromechanical devices on the the cycle a blade on the keyboard printer, such as, the backspace, tab, index, return, shift and lock mechanisms as well as the character selection forming no part of the present invention, this logic control circuitry, not shown, will provide for switch whetting, low-impedance ties to a specified logic voltage, and also provide the necessary amplification and suppression to operate the solenoids under logic control. A magnet driver 64 is provided for each solenoid to supply the necessary voltage to operate each solenoid in response to a pulse applied to the driver from a remote point, such as, from a paper or magnetic tape unit.

The solenoid assembly may comprise a series of either six or seven solenoids to control actuation of the selector latches L, depending upon whether a seventh selector latch is utilized as a code check. In the arrangement shown, six solenoids 50 are utilized to control actuation of six rotational and tilt selector latches L, and a seventh solenoid 50' is operative to control movement of a latch, not shown, which pulls down on the cycle bail 29 to release the cycle clutch for rotation of the cycle shaft 35 through each pring cycle as described.

In order to control the duration of time that each solenoid is energized in a print cycle, a magnetically actuated switch 70 mounted on the main power frame F in adjacent, spaced relation to one end of the filter shaft 40. The magnetic switch includes a reed switch 72 and magnet 73 separated by a narrow gap 74, the reed switch being electrically connected in the logic control circuit for the magnet drivers. A vane 75 is mounted on the end of the filter shaft 40 and is provided with a pair of diametrically opposed blades 76 and 77 being aligned for rotational movement through the gap 74 between the magnet 73 and reed 72. In each 180 print cycle one of the filter blades will pass through the gap to interrupt the circuit established from the magnet drivers to the solenoids 50 thereby deenergizing the solenoids and permitting return of the selector latches to the forward position. As shown in FIGS. 2 and 4, dimensioning or sizing of the width of the blades 76 and 77 will determine and limit the period of energization of the solenoids in each cycle. For example, the blades may be correlated with rotation of the cycle shaft 35 to permit the switch to close at 30 to 60 into each printing cycle to energize the solenoids, then to deenergize the solenoids upon passage of the blade across the gap at l 15 to from the beginning of the cycle and well in advance of the end of the print cycle. The blade will remain in the gap to interrupt the circuit through 30 to 60 into the next cycle. Thus the solenoid can be accurately picked or energized, over a limited phase of the cycle necessary to remove a selected combination of latches L from the path of the bail 26, and thereafter deenergized to remove any residual magnetism and restore the latches L for each next cycle in succession. This results in close accurate control over the movement of the latches while permitting high-speed printing in a reliable efficient manner.

In a typical logic circuit designed to effect the necessary control over each automatic print cycle, each character to be printed is coded in a well-known manner and, for example, may be applied serially in the form of bits into a shift register. After the last bit representing a character is clocked into the shift register, the bits are loaded in parallel into a storage register and a clock circuit is simultaneously activated to set or reset a bistable device controlling a second clock circuit, such as, a one-shot delay. If the printer mechanism is in condition to receive, as controlled generally by an interlock switch on the printer, the one-shot delay is activated and the solenoid 50' is energized to initiate each print cycle by releasing the cycle shaft for rotation of the filter shaft 38 and associated vane 75. The terminal leads 72' on the reed switch 72 are connected into the second clock circuit to control the period of energization of the solenoids 50 in each cycle. Thus, when the one-shot delay is activated in the second clock circuit energizing pulses are not gated to energize the magnet drivers until the filter switch is permitted to close at 30 to 60 into the cycle and are not deenergized until the switch is opened at some time later in the cycle. If for any reason the filter switch should fail to properly function in each cycle, timing out of the second clock circuit, or delay, at the end of the cycle will deenergize the solenoids. Of course, energizing pulses are applied only to selected magnet drivers corresponding to the combination of bits in the storage register in each print cycle. Again the specific circuit described to control the solenoids is more for the purpose of illustration and not limitation, and forms no part of the present invention.

From the foregoing the present invention will be seen to comprise an electromagnetic character selection unit being especially adaptable for use in controlling a single element print head to advance different characters into printing position by selective actuation of a plurality of latch members associated with a displacement mechanism for the head. The solenoids in the selection unit are characterized by their ability to actuate the latches over a limited time interval of each print cycle under the control of an electronic switch which is correlated in opening and closing with the print cycle timer member, or cycle shaft, so that the solenoids can be deenergized well in advance of the end of the print cycle. In this way, the latches are restored ahead of the next cycle without the use of separate holddown or restoring mechanisms. It will be apparent that the filter switch may be electronically interconnected directly into other types of control circuits "than that described in order to logically control the solenoids and other functions of the keyboard printer.

lt is understood that various modifications and changes in the construction and arrangement of parts and elements comprising the preferred forrn of invention may be resorted to without departing from the spirit ofthe present invention.

What is claimed is:

1. In an electromagnetic character selection unit for a keyboard printer having a print element in which a printing cycle is initiated for selecting and printing a character on the print element, the print element being advanced to present a selected character for printing in each printing cycle by actuation of selected combinations of control links representing each character, means regulating the duration of each printing cycle, and the pring element and control links being returned to inactive positions in each printing cycle in preparation for each next printing cycle in succession, said control links normally being biased to the inactive position, the combination comprising:

electrical signal generating means operative to present a coded combination of electrical signals representing a character to be printed at the beginning of each printing cycle,

a plurality of electromagnets each energizable by an electrical signal from said electrical signal generating means, there being one electromagnet for each of said control links,

mounting means for mounting said electromagnets in spaced relation to said control links, said mounting means being provided with opposite side portions projecting beyond one end of each electromagnet,

an armature plate extending from connection to each control link through aligned slots in said side portions in normally spaced relation across the end of each electromagnet, each said plate being pivotal about a side portion nearest its associated control link in response to energization of an electromagnet to overcome the biasing of said control link whereby a selected combination of control links are activated in each printing cycle to print a character in response to each of the coded combination of signals applied to said electromagnets, and

electrical control means to regulate the period of energization of said electromagnets during each printing cycle, said electrical control means being defined by a magnet driver to energize each of said electromagnets, and'a magnetic switch common to said drivers having a reed switch, a magnet and a filter blade movable through a slot between said magnet and switch to interrupt the circuit between said magnet drivers and said e lectromagnets, said armature plates being restored by said contro lmks to their normally inactive position upon deenergizing said electromagnets without independent means of restoration of said armature plates.

2. In an electromagnetic character selection unit according to claim 1, said mounting means defined by a common frame for said electromagnets, said frame being generally U-shaped and having extension plates on each side portion provided with the aligned slots to receive the free end of each armature plate.

3. In an electromagnetic character selection unit according to claim 2, said slots being of generally rectangular configuration and disposed at the side edges of the frame, said slots being enlarged with respect to said plates to permit limited movement of each plate within each aligned pair of said slots.

4. In an electromagnetic character selection unit according to claim 3, the free end of each plate being offset from the end of the plate connected to each control link, and a spacer member interconnecting each control link and plate.

5. An electromagnetic character selection unit adapted to selectively advance selected ones of a series of interposer rods between a normally inactive position and an active position in advancing different selected characters on a pring head into printing position, said unit comprising:

a solenoid for each of said interposer rods,

a common, U-shaped frame assembly mounting said solenoids in spaced parallel relation to said interposer rods, said frame assembly having opposite side portions extending beyond the open ends of said solenoids and side extension plates projecting beyond the edges of said side portions with aligned slots in said extension plates on opposite sides of each of said solenoids,

an armature plate connected to each of said interposer rods and extending transversely therefrom for insertion through a pair of aligned slots in spaced relation to the end of a solenoid, selected plates being pivotal about the ends of the side portions nearest said interposer rods in response to energization of selected ones of said solenoids to activate their associated interposer rods for advancing a character to the printing position, and

electrical control means defined by a magnet driver for energizing each of said solenoids, and a magnetic switch common to said drivers having a reed switch, a magnet and a filter blade movable through a slot between said magnet and switch to interrupt the circuit between said magnet drivers and said solenoids to regulate the period of energization of said solenoids. 

1. In an electromagnetic character selection unit for a keyboard printer having a print element in which a printing cycle is initiated for selecting and printing a character on the print element, the print element being advanced to present a selected character for printing in each printing cycle by actuation of selected combinations of control links representing each character, means regulating the duration of each printing cycle, and the print element and control links being returned to inactive positions in each printing cycle in preparation for each next printing cycle in succession, said control links normally being biased to the inactive position, the combination comprising: electrical signal generating means operative to present a coded combination of electrical signals representing a character to be printed at the beginning of each printing cycle, a plurality of electromagnets each energizable by an electrical signal from said electrical signal generating means, there being one electromagnet for each of said control links, mounting means for mounting said electromagnets in spaced relation to said control links, said mounting means being provided with opposite side portions projecting beyond one end of each electromagnet, an armature plate extending from connection to each control link through aligned slots in said side portions in normally spaced relation across the end of each electromagnet, each said plate being pivotal about a side portion nearest its associated control link in response to energization of an electromagnet to overcome the biasing of said control link whereby a selected combination of control links are activated in each printing cycle to print a character in response to each of the coded combination of signals applied to said electromagnets, and electrical control means to regulate the period of energization of said electromagnets during each printing cycle, said electrical control means being defined by a magnet driver to energize each of said electromagnets, and a magnetic switch common to said drivers having a reed switch, a magnet and a filter blade movable through a slot between said magnet and switch to interrupt the circuit between said magnet drivers and said electromagnets, said armature plates being restored by said control links to their normally inactive position upon deenergizing said electromagnets without independent means of restoration of said armature plates.
 2. In an electromagnetic character selection unit according to claim 1, said mounting means defined by a common frame for said electromagnets, said frame being generally U-shaped and having extension plates on each side portion provided with the aligned slots to receive the free end of each armature plate.
 3. In an electromagnetic character selection unit according to claim 2, said slots being of generally rectangular configuration and disposed at the side edges of the frame, said slots being enlarged with respect to said plates to permit limited movement of each plate within each aligned pair of said slots.
 4. In an electromagnetic character selection unit according to claim 3, the free end of each plate being offset from the end of the plate connected to each control link, and a spacer member interconnecting each control link and plate.
 5. An electromagnetic character selection unit adapted to selectively advance selected ones of a series of interposer rods between a normally inactive position and an active position in advancing different selected characters on a pring head into printing position, said unit comprising: a solenoid for each of said interposer rods, a common, U-shaped frame assembly mounting said solenoids in spaced parallel relation to said interposer rods, said frame assembly having opposite side portions extending beyond the open ends of said solenoids and side extension plates projecting beyond the edges of said side portions with aligned slots in said extension plates on opposite sides of each of said solenoids, an armature plate connected to each of said interposer rods and extending transversely therefrom for insertion through a pair of aligned slots in spaced relation to the end of a solenoid, selected plates being pivotal about the ends of the side portions nearest said interposer rods in response to energization of selected ones of said solenoids to activate their associated interposer rods for advancing a character to the printing position, and electrical control means defined by a magnet driver for energizing each of said solenoids, and a magnetic switch common to said drivers having a reed switch, a magnet and a filter blade movable through a slot between said magnet and switch to interrupt the circuit between said magnet drivers and said solenoids to regulate the period of energization of said solenoids. 